Reproducing in vitro the physiological characteristics of brain vascular segments represents a critical issue. Adequate modeling of the cerebrovasculature could significantly help understand the mechanisms and improve the pharmacology of disease where a role for leukocytes migrating across the cerebrovasculature is demonstrated. Thanks to the previous support (Phase I) we were able to prototype and test drive a new dynamic in vitro model of the BBB (DIV- BBB) permissive for leukocyte extravasation. Our initial effort aimed at piercing hollow fibers in a reproducible manner; the results were recently published. We found that manually perforated hollow fibers allow leukocytes passage across the BBB in response to pro-inflammatory stimuli and hemodynamic changes. We were also able to produce a capillary-venule segment by varying the rheological parameters (e.g., changing the shear stress) of the system. In addition we recently developed a system to mechanically stretch the hollow fibers increasing the pore size up to the physiologically relevant size of ~5 m. Controlled traction was applied to the end of the fibers and scanning electron microscopy showed enlarged pores within the stretched fiber. To further the commercial opportunity afforded by this new BBB model, we propose the following Phase II Specific Aims: To optimize the performance of a dynamic in vitro capillary-venules model of the brain cerebrovasculature permissive for leukocyte extravasation. To determine the pattern of leukocytes extravasation in control and diseased capillary-venules segments composed of fibers with different transmural permeability properties (from Aim 1). To compare the results obtained using these DIV- BBB models to other state-of-art in vitro BBB models. We will initially tailor the use of the DIV capillary-venules system to multiple sclerosis and epilepsy research and drug development. We have assembled a multi-disciplinary team of investigators and experts in the field of leukocyte migration across the cerebrovasculature. Additional clinically relevant venues are detailed in the Commercialization Plan. Given our preliminary results and the confirmatory progress report described in detail in this application, and given the fact that i the meantime development of new drugs has remained a major issue in the treatment of neurological diseases, we believe that the combination of a strong record of accomplishment and sound experimental design aimed at improving drug development are fundamental aspects of this Phase 2 proposal.